Booster-type compressor

ABSTRACT

A compressed gas is introduced into a casing. A piston pivotally connected to a reciprocating mechanism moves up and down in a cylinder. The compressed gas in the casing is sent to a space on the piston through a groove formed in the inner circumference of the cylinder and is further compressed in the space by the piston.

BACKGROUND OF THE INVENTION

The present invention relates to a booster-type compressor that compresses a compressed gas with a reciprocating piston.

A conventional booster-type compressor is shown in FIG. 2, in which a suction check valve 23 is formed at one side of a top wall 22 of a cylinder 21 and a discharge check valve 24 is formed at the other side of the top wall 22. A suction chamber 26 which has an inlet 25 and a discharge chamber 28 which has an outlet 27 are formed on the suction check valve 23 and discharge check valve 24 respectively. A crank shaft 31 integrally connected to a drive shaft 30 driven by an external power source is provided in a crankcase 29 under the cylinder 21. A piston 33 in the cylinder 21 is reciprocated by the crank shaft 31 via a piston rod 32. A compressed gas such as N₂ sucked from the inlet 25 is guided into a space on the piston 33 via the suction check valve 23, compressed and discharged via the discharge check valve 24 and outlet 27. Such a compressor is known.

In such a booster-type compressor, with reciprocation of the piston 33, the compressed gas which flows into a space on the piston 33 in the cylinder 21 partially leaks via a gap between the outer circumferential wall of the piston 33 and the inner circumferential wall of the cylinder 21 into the crankcase 29.

The compressed gas into the crankcase 29 is partially released to the air. If it is toxic, it will cause environmental contamination.

In a suction process of restarting or non-load operation of the booster-type compressor, the compression chamber is decompressed, so that air introduced through the air hole 34 of the crankcase 29 flows into the space on the piston 33 through the gap on the outer circumference of the piston 33 to mix with the compressed gas from the inlet 25 to make its concentration fallen.

To overcome the problem in the booster-type compressor, the air hole 34 of the crankcase 29 is closed, but the sealed crankcase 29 raises the temperature therein with the operation to damage bearings 35, 36 and a seal 37 for the drive shaft 30 and crank shaft 31.

SUMMARY OF THE INVENTION

In view of the disadvantages above, it is an object of the present invention to provide a booster-type compressor in which a compressed gas is further compressed in a space on a piston moved up and down by a reciprocating mechanism to prevent the compressed gas from leaking back into a casing including the reciprocating mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the invention will become more apparent from the following description with respect to embodiments as shown in accompanying drawings wherein:

FIG. 1 is a vertical sectional view of a booster-type compressor according to the present invention; and

FIG. 2 is a vertical sectional view of a conventional booster-type compressor.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

A booster-type compressor according to the present invention will be described with respect to FIG. 1.

A discharge check valve 4 is provided in a top wall 3 of a cylinder 2 at the upper part of a crankcase 1 and there is a discharge chamber 6 having a discharge hole 5 above the top wall 3.

In the crankcase 1, a drive shaft 8 integrally connected to a crank shaft 7 and driven by a suitable power is pivotally mounted via bearings 9, 9 and a seal 10. A piston rod 12 is pivotally connected to the crank shaft 7 via a bearing 11 at one end, and is pivotally connected to a piston 13 in the cylinder 2 at the other end.

In the inner circumference of the cylinder 2, a gas-guiding groove 14 is formed. The lower end of the gas-guiding groove 14 communicates with the inside of the crankcase 1 and the upper end of the gas-guiding groove 14 communicates with a space on the piston 13 in the cylinder 2 when the piston 13 is in the lowest position. When the piston 13 rises, the gas-guiding groove 14 is closed by the piston 13.

A piston ring engaged in a piston-ring groove of the piston 13 plays a role of a check valve.

A compressed gas supply tube 15 is connected to the crankcase 1.

The discharge check valve 4 is not opened with the pressure of compressed gas in the crankcase 1, but is allowed to open when the piston 13 rises to compress the gas in the space.

By the drive shaft 8, the piston 13 is reciprocated, so that a compressed gas in the crankcase 1 is forwarded to the space on the piston 13 via the gas-guiding groove 14, compressed and discharged to the outside via the check valve 4 and the discharge hole 5.

Instead of the groove 14 and piston ring, there may be a check valve which opens only to the chamber in the piston 13.

The foregoing merely relates to an embodiment of the invention. Various changes and modifications may be made by persons skilled in the art departing from the scope of claims wherein: 

1. A booster-type compressor comprising: a cylinder; a casing having a compressed-gas supply tube through which a compressed gas is introduced into the casing; a piston moving up and down in the cylinder, a gas-guiding groove being formed in a lower part of an inner circumference of the cylinder to allow the compressed gas to move into a space from the casing on the piston via the gas-guiding groove between an outer circumference of the piston and the inner circumference of the cylinder when the piston moves down, the compressed gas being prevented from flowing into the space when the piston moves up to further compress the compressed gas; and a reciprocating mechanism for moving the piston up and down.
 2. The booster-type compressor of claim 1 wherein the reciprocating mechanism comprises a crank shaft pivotally mounted to a piston rod fixed to the piston; and a drive shaft integrally connected to the crank shaft and driven by a power source.
 3. The booster-type compressor of claim 1 wherein a discharge check valve is provided in a wall of the cylinder to allow the compressed gas to go out of the space in the cylinder.
 4. The booster-type compressor of claim 3 wherein the discharge check valve is opened only when the compressed gas is further compressed by the piston.
 5. The booster-type compressor of claim 1 wherein the compressed gas comprises an inert gas.
 6. The booster-type compressor of claim 5 wherein the inert gas comprises N₂. 